• 한국해양학회지
• /
• v.23 no.3
• /
• pp.130-145
• /
• 1988

Spatial distribution and temporal variations of phytoplankton population were investigated in Ch$\check{o}$nsu Bay, the Korean western coast. Diurnal fluctuations of phytoplankton standing crop are associated with semidiurnal tidal cycle, as high concentration at low tide and low at high tide. In monthly variations of phytopolankton standing crop, the 1st peak occurrs in March and the 2nd one in August. The study area could be divided into two parts, outer bay and inner bay according to the physical and biological factors such as water temperature and salinity, and phytoplankton distribution patterns. The northern waters of the bay, however, may be affected by irregular fresh water influx through the lock of the dike. Because of the hydrographical differences among the surveyed stations, phytoplankton species succession patterns of each station have some differences. On the whole in this study area, Paralia sulcata and Skeletonema costatum are dominant species all the year round. However, except June, Paralia sulcata, a tychopelagic diatom is not dominant species at Station 6 (northern end of the bay). This seems to be caused by the fact that the waters of northern part of the bay is less turbulent than that of the outer bay. The result of principal component analysis (PCA) indicates that Ch$\check{o}$nsu Bay is normal coastal ecosystem where the environmental conditions are cycled in a year, and water temperature and nitrogenous nutrients such as nitrate, nitrite and ammonia are major factors to influence the annual cycle of environmental conditions.

• Journal of Wetlands Research
• /
• v.22 no.4
• /
• pp.286-294
• /
• 2020

This study aims to economically evaluate rice production and various ecological services provided by organic rice paddy carrying out rice-fish mixed farming. It was also conducted to find a stable structure for increasing the income of rice-producing farmers and promoting ecological services by evaluating the economic feasibility of organic rice paddy for rice-fish mixed farming. As a result of the analysis of expected effects by ecological service functions according to the types of agriculture in the rice-fish mixed farming, general conventional paddy fields were evaluated to have an effect of continuously decreasing biodiversity such as amphibian reptiles, aquatic insects, bird habitats, experience and ecological education, and vegetation diversity, while the biodiversity of organic and rice-fish mixed paddy fields was assessed to increase. As a result of evaluating the economic value, as the area for fish production increases compared to the common practice and organic paddy fields, rice production decreases, but fish production increases and total income was analyzed to increase. In addition, if the value of ecosystem service functions is assessed in the future, it will increase further. It is hoped that these findings will be used as basic data for solving oversupply problems in the rice industry, preserving safe farm income, and improving sustainable farming and ecosystem service functions.

• Membrane Journal
• /
• v.25 no.2
• /
• pp.132-143
• /
• 2015

Water is an essential resource for humans, but fresh water becomes scarce due to population growth and contamination of limited resources. Membrane technology has been widely used for water treatment, and forward osmosis is a process which does not need high hydraulic pressure for the operation. However, there are needs for (1) development of novel draw solutes causing low internal concentration polarization and reverse salt flux for high water flux, and (2) development of economic recovery method of the draw solutes in the diluted draw solution. Previous researches on the draw solute include $NaHCO_3$ which can be regenerated by about $60^{\circ}C$ heating, sucrose which can make potable water without additional process, and magnetic nanoparticles which can be regenerated by external magnetic field. Using the principles of forward osmosis process, sea water desalination, wastewater treatment, refinement of proteins, energy generation using pressure retarded osmosis process, preparation of diluted fertilizer, and growing algae for biofuel can be conducted. This paper summarizes characteristics of ideal draw solutes, recovery method of the draw solutes, and various application examples.

• Journal of Wetlands Research
• /
• v.8 no.3
• /
• pp.67-77
• /
• 2006

Sedimentological investigations on surface and suspended sediments were performed in Masan Bay of the South Sea in order to reveal recent changes in depositional environments concerning anthropogenic influence. Surface sediments had been classified as 3 sediment facies: mud, slightly gravelly mud, and gravelly mud. In general, mud facies with more than 60% of silt is predominant and slightly gravelly mud facies occurs at the watercourse of bay's central area. The silt-dominant mud faices appears to be predominant before and after dredging. Temperature and salinity changes during one tidal cycle for each season suggest that water columns were stratified without vertical mixing regardless of the season due to weak intensity of tide from the effect of geographical features. The effect of freshwater discharge from the land seems to be insignificant. The strongest current was observed during ebb tide in spring and autumn while observed during flood tide in summer and winter. Net sediment flux (fs) and net suspended sediment transport (Qs) for suspended sediment were determined by remaining drift developed here. Net suspended sediment transport loads were seaward with $62.02{\times}10^3kgm^{-1}$, $31.84{\times}10^3kgm^{-1}$ in spring and fall, respectively, and landward with $18.23{\times}10^3kgm^{-1}$, $3.22{\times}10^3kgm^{-1}$ in summer and winter, respectively.

• Korean Journal of Ecology and Environment
• /
• v.53 no.4
• /
• pp.344-354
• /
• 2020

Identification of the target species of 2-MIB (2-methyllisoborneol) production is crucial in the management of off-flavor problem in the freshwater system. This study was conducted to identify 2-MIB-producing Pseudanabaena strains occurring in the North Han River system using molecular genetic method. Eleven phenotypes of Pseudanabaena were isolated from several mainstream sites of the North Han River, including Sambong-ri, Joam-myun, and Lake Uiam areas. Despite of morphological similarity of the strains, the phylogenetic analysis using 16S rDNA classified them into different species with low genetic similarity (40~55%). Isolated Pseudanabaena strains were converged to four species; Pseudanabaena cinerea, P. yagii, P. mucicola, and P. redekei. Among them, the 2-MIB synthesizing gene (mibC) was detected in P. cinerea, P. yagii, and P. redekei. However, actual 2-MIB production was detected only in P. cinerea and P. redekei based on gas chromatography analysis. This study is the first report of the molecular identification of Pseudanabaena strains and their 2-MIB production potential in Korea. The results of this study provides an evidence of species diversity of Pseudanabaena occurring in the North Han River.

• Journal of Marine Bioscience and Biotechnology
• /
• v.15 no.2
• /
• pp.41-48
• /
• 2023

The objective of the present study was to improve the biomass productivity of newly isolated freshwater green microalga Parachlorella sp. This was accomplished by culture conditions optimization, including CO₂ concentration, superficial gas velocity, and light intensity, in 0.5 L bubble column photobioreactors. The supplied CO₂ concentration and gas velocity varied from 0.032% (air) to 10% and 0.02 m/s - 0.11 m/s, respectively, to evaluate their effects on growth kinetics. Next, to maximize the production rate of Parachlorella sp., a lumostatic operation based on a specific light uptake rate (q_e) was applied. From these results, the optimal CO₂ concentration in the supplied gas and the gas velocity were determined to be 5% and 0.064 m/s, respectively. For the lumostatic operation at 10.2 µmol/g/s, biomass productivity and photon yield showed significant increases of 83% and 66%, respectively, relative to cultures under constant light intensity. These results indicate that the biomass productivity of Parachlorella sp. can be improved by optimizing gas properties and light control as cell concentrations vary over time.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.28 no.4
• /
• pp.475-488
• /
• 1995

In order to see the seasonal variation of nutrients and the limiting factors to the primary production in Deukryang Bay, both dissolved inorganic nutrients and salinity were measured in the surface waters during the periods from July 1992 to March 1993. The mean value of salinity was the lowest in ?all and the highest in early spring. Dissolved inorganic nitrogen (DIN) was the highest in winter and the lowest in summer. However, both phosphate and silicate were the highest in summer and the lowest in fall. Salinity was generally higher in the outer region than in the inner region of the bay.DIN content was nearly depleted (less than $2{\mu}M$) in summer. From fall to spring, DIN content was nearly depleted in the inner region and relatively high in the outer region of the Day. Phosphate was the highest in summer showing an opposite distribution pattern to salinity, and it was nearly depleted (less than $0.1{\mu}M$) in fall and winter. In spring, however, phosphate content was slightly high in the outer region. Silicate content showed an opposite distribution pattern to salinity in summer. in other seasons, However, the distribution pattern of silicate was similar to the salinity. DIN seemed to be a limiting factor for the primary production at all area of the bay in summer and at the inner region in other season. However, phosphate seemed to be a limiting factor at all area of the bay in fall and winter and at the inner region in spring. Silicate may limit the production of diatoms at the inner region of the bay in winter and spying. Both phosphate and silicate showed a good inverse relationship with salinity in summer, which indicates inputs of these nutrients from the freshwater runoff. In the other seasons, both nitrate and silicate showed a positive linear relationship with salinity in the outer region of the bay, suggesting that these two nutrients were mainly supplied by the inflow of the offshore costal water which had high nitrate content associated with vertical mixing.

• Korean Journal of Ecology and Environment
• /
• v.35 no.2 s.98
• /
• pp.92-102
• /
• 2002

This study was conducted to compare filtering abilities of three species of freshwater mussels (Cobicula fluminea, Corbicula leana and Unio douglasiae) and to evaluate their filter feeding effects on water quality change in experimental enclosure systems. Mussel feeding in both laboratory and enclosure resulted in decrease of particulate material, such as chlorophyll, total P, SS. In the treatment with 600 individuals of mussels, chllorophyll concentration and net primary productivity decreased from $87.3{\pm}4.5\;{\mu}g/L$ and $106.3{\pm}8.8\;{\mu}gC\;L^{-1}\;hr^{-1}$ to nearly the same level as the mussel-free enclosure ($25.0{\pm}0.5\;{\mu}g/L$ and $15.6{\pm}13.3\;{\mu}gC\;L^{-1}\;hr^{-1}$, respectively)(P< 0.05, n = 6, ANOVA). In concert with the decrease of chlorophyll concentration, not only was the transparency enhanced from 0.48 m to 1.2m but also the suspended solids and total phosphorus decreased from $22.0{\pm}1.0\;mg/L$ to $7.5{\pm}0.5\;mg/L$ and $133{\pm}0.8\;{\mu}g/L$ to $70{\pm}0.0\;{\mu}g/L$, respectively (P<0.001, $r^2$>0.71, n = 11). Although slight decrease of SRP concentration and the increase of inorganic nitrogen ($NH_3-N$ and $NO_2-N$) were observed in the mussel addition enclosure, there was no statistical difference between two enclosures. Based on the filtering rate on phytoplankton and nutrient release rate in forms of feces and pseudofeces, Corbicula leana appeared to be the most efficient filter-feeder among three mussel species. These results inidicate that Cobicula play an important role in controlling particulate sestons and thus it could be applied as a biocontroler for the water quality management in lakes and reservoirs with algal blooms.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.51 no.3
• /
• pp.1-20
• /
• 2023

The present study has monitored the changes in the biodiversity of Dunchon-Dong ecological and landscape conservation area after the restoration of the wetland, identified and analyzed the threats to the ecosystem, and presented a management plan accordingly. In this area which was forests and rice paddies in the past, apartment reconstruction is currently underway, with some hinterland forests and wetlands remaining. When we look into the change in the floras, the total number of species was 193 in 2000 before the restoration, it decreased from 2004 to 2006, and as of 2019, it was 149, showing an increasing trend. The result of comparing the species that emerged before and after the restoration showed an increase in Cyperaceae herbs such as Carex maximowiczii and Carex dispalata growing in wetland areas within forests and Schoenoplectiella juncoides and Schoenoplectus tabernaemontani growing in areas within wetlands where shallow water is maintained. As a result of analyzing the change in the area ratio of each type of extant vegetation, the wetland native herbs formed the power at the highest ratio after the restoration. The change in the power of the wetland native herbs was on an increasing trend until 2007, after which it decreased much in 2010 and then gradually increased, showing values of 26.6% in 2000, 44.6% in 2002, 49.0% in 2005, 53.3% in 2007, 28.7% in 2010, and 37.3% in 2019. The cause of the decrease in 2010 was judged to be due to the vegetation management conducted to secure open water and remove organic matter in freshwater reservoirs. The amphibia which emerged from 2000 to 2019 was a total of 9 species including Hynobius leeshii, Bufo gargarizans, Kaloula borealis, and Rana uenoi. As a result of the changes in the emerging wild birds, the species diversity index before the restoration was 0.9922 in 2000, and the species diversity index after the restoration gradually increased to 1.2449 in 2005, 1.2467 in 2010, and 2.2631 in 2019. The amphibia and wild birds inhibiting in the Dunchon-Dong forest and wetland were judged to have increased through continuous wetland maintenance such as naturalized plant removal management, native plant maintenance, and open water securing management. For the ecosystem preservation management of the Dunchon-Dong ecological and landscape conservation area, it was suggested to minimize the impact of the Dunchon-Dong reconstruction project, reorganize the indiscriminate access roads adjacent to the wetland, and reorganize the main entrance to the wetland. For ecosystem restoration management, systematic restoration and ecological buffer planting were suggested to be carried out at the time of construction fence demolition.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.25 no.6
• /
• pp.687-697
• /
• 2019

By monitoring sediment grain size and level variation of tidal flat surface for 6 years (2005-2011), and also by mooring TISDOS (tidal-flat sediment dynamics observation system) on the low intertidal flat in 2008, we investigated the sedimentary environment of tidal flat in the dammed Yeongsan River Estuary. The tidal flat of the Yeongsan River Estuary lost 82 % of its area because of coastal development projects, and a narrow tidal flat below mean sea level now remains. Most of the tidal flat sediments are composed of silt up to 70-94 %, and show the characteristics of clay deficiency and silt dominance. This is closely related with the coastal development, which led to the destruction of high tidal flats where most mud settled, and the modification of tidal current patterns. Moreover, the estuarine tidal-flat sediments reveal seasonal variation. They are coarse with abundant silt during windy autumn to spring, fine with abundant clay during the less-windy and high-discharge summer. This phenomenon indicates that the behavior of sediment particles on the low intertidal flats of the Yeongsan River Estuary is influenced by wind waves for silt and fresh water discharge and the tidal process for clay. Monitoring results of the altitude of tidal flat surface showed that the study area had eroded at an average rate of -2.6 cm/y during the period of 2005-2011, and also that an unusual deposition with a rate of 4 cm/y occurred in 2010. The erosion can be explained by an increased tidal amplitude and a strengthened ebb-dominant tidal asymmetry after the construction of an estuary dike and the Yeongam Kumho Seawall. The deposition in 2010 seems to have been closely related to the mass production of suspended materials from dredging of the estuary.